Huge telescope will struggle to find extraterrestrial life

The largest radio telescope ever to be constructed will struggle to listen in on extra-terrestrial civilizations like our own, according to two astronomers in the UK. Their calculations suggest that when the Square Kilometre Array (SKA) starts work in 2022 it will find it difficult to tune into radio signals from alien civilizations with Earth-like technology. The finding, they say, is further evidence that scientists must take a multidisciplinary approach to the hunt for intelligent life that doesn't just rely on detecting radio signals.

The Search for Extra-Terrestrial Intelligence (SETI) has been patiently eavesdropping on the galaxy for potential alien signals for over 50 years, so far without success. As one of its many scientific objectives, the SKA will join the search in 2022, hoping to answer the age-old question of whether our civilization really is unique.

However, research by Duncan Forgan, at the University of Edinburgh, and Bob Nichol, at the University of Portsmouth, suggest that its chances of finding human-like civilizations are slim: just one in 10 million.

They built a computer model of a mock Milky Way galaxy to see how many intelligent civilizations it could likely support. "We wanted to give as strong as an assessment as we could for using the latest radio telescopes for SETI," Forgan told physicsworld.com. The pair threw into the mixing pot the latest data on, among other things, stellar evolution, planetary system formation and habitable zones – the area around a star warm enough for a planet to have liquid water on its the surface.

10,000 civilizations per galaxy

To calculate the best-case scenario for SKA success, they optimistically assumed that if an Earth like planet sits in the habitable zone it would always go on to host intelligent life. From this they were able to populate the galaxy with intelligent life by assigning stars random properties from a statistical distribution. Having run the model 30 times they found the average galaxy would be home to about 10,000 intelligent civilizations.

"We now have a data set of galactic civilizations over time and space," said Forgan. "But there are factors which can prevent a civilization from being eavesdropped on: the civilization could destroy itself or be extinguished by an asteroid impact. However, more likely is that an advance in technology could make them harder to detect, " he added.

On Earth, we have been leaking radio signals into space for almost a century and any nearby civilization could eavesdrop on our signals. Indeed SKA could detect us if it were placed anywhere up to 100 parsecs – 326 light-years – away. However, as our technology is improving, and the power required to generate such signals is decreasing, we are moving from a "radio loud" to a "radio quiet" planet.

Too old for loud radio

With these factors in mind Forgan and Nichol combined their galactic population findings with the constraints on mass extinction, based on the Earth's fossil record, and the idea that a civilization is only "radio loud" for its first 100 years. They found the chances of radio communication between us and an Earth-like or a short-lived civilization, within the 100 parsec sensitivity limit of the SKA, to be one in 10 million.

However, this finding only applies to civilizations with technology akin to our own; it does not rule out stumbling across signals from a more highly developed civilization. "This is only one small part of SETI. Other SETI searches work on the assumption that they are looking for longer lived civilizations that emit, for whatever purpose of their own, rather stronger radiation," stressed Alan Penny, a SETI researcher at the University of St Andrews.

Forgan would like to see more resources put into other methods to sit alongside and complement conventional radio SETI searches. "The way we are approaching SETI is quite one-dimensional. There will always be a place for radio communication but we are getting close to its limit and we should find other ways to try as well," he said.

The research has been accepted for publication in the International Journal of Astrobiology and a preprint is available on arXiv.

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

It's about SKA sensitivity - it could detect our own signals from about three times the distance they traveled so far.

But well... there's not so many stars in a ball of 100 light year radius around us and even if the 10.000 civillizations per galaxy were really there at the same time the chances one of them is near a star so close to us are slim.

telepathic communication

Does anyone ever consider the possibility that most of the long range communication is taken place telepathically (maybe exploiting non-local connections that any intelligent being can learn to make use of if given the opportunity)? Evolutionary pressures have not forced us to evolve any type of "receiver" in our brains that is strong enough naturally to pick up on such communication, but I wonder if we can learn to tune in.

I would like to investigate this issue more rigorously at some point, but for now, I think it is worth pointing out that since communication with EM wave does not work very well, and since intelligent beings will likely discover Quantum Physics, most of them may abandon attempts to contact other species via EM waves, and may learn some other form of communication that allows for more immediate (or non-local) exchanges.

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

It's about SKA sensitivity - it could detect our own signals from about three times the distance they traveled so far.

I think it has no sense. Sensitivity is the capability to detect a signal, but the signal must arrive first to the location to be detected! I agree with mryan2010. We've been broadcasting radio signals for about 100 years: this means that the oldest signal is at 100 light years from us now.

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

It's about SKA sensitivity - it could detect our own signals from about three times the distance they traveled so far.

I think it has no sense. Sensitivity is the capability to detect a signal, but the signal must arrive first to the location to be detected! I agree with mryan2010. We've been broadcasting radio signals for about 100 years: this means that the oldest signal is at 100 light years from us now.

Well, the placement of the sentence in the article is misleading, but it is, as Kasuha stated, referring to the sensitivity of the telescope -- if somehow you place the same set-up, 226 years later, at a distance of 326 ly from Earth, the telescope will be able to detect the earliest radio transmissions. However, placing it farther, it may not be able to do so.

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

It's about SKA sensitivity - it could detect our own signals from about three times the distance they traveled so far.

I think it has no sense. Sensitivity is the capability to detect a signal, but the signal must arrive first to the location to be detected! I agree with mryan2010. We've been broadcasting radio signals for about 100 years: this means that the oldest signal is at 100 light years from us now.

Well, the placement of the sentence in the article is misleading, but it is, as Kasuha stated, referring to the sensitivity of the telescope -- if somehow you place the same set-up, 226 years later, at a distance of 326 ly from Earth, the telescope will be able to detect the earliest radio transmissions. However, placing it farther, it may not be able to do so.

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

It's about SKA sensitivity - it could detect our own signals from about three times the distance they traveled so far.

I think it has no sense. Sensitivity is the capability to detect a signal, but the signal must arrive first to the location to be detected! I agree with mryan2010. We've been broadcasting radio signals for about 100 years: this means that the oldest signal is at 100 light years from us now.

Well, the placement of the sentence in the article is misleading, but it is, as Kasuha stated, referring to the sensitivity of the telescope -- if somehow you place the same set-up, 226 years later, at a distance of 326 ly from Earth, the telescope will be able to detect the earliest radio transmissions. However, placing it farther, it may not be able to do so.

Much of this research is really quite meaningless as it assumes that there will be a civilisation relatively close to the earth that is at the same, or more advanced, evolutionary point. If a civilisation is only 2500 years behind us, less than an eye blink in cosmological times, then they will be in the stone age and not really interested in radio though they will have the silicon chip albeit in a slightly different form :-) .

Even if life does exist within this finite range it will not necessarily be "intelligent". The dinosaurs would still be ruling this planet had it not been for an unfortunate meeting with a space borne lump of rock that let the underlings evolve.

So with a total number of predicated life supporting systems set at 10000 randomly seeded around our galaxy at various stages of development it seems that to search for them is a waste of time, money and man/woman power. Surely there are more beneficial lines of research that should be followed.

Much of this research is really quite meaningless as it assumes that there will be a civilisation relatively close to the earth that is at the same, or more advanced, evolutionary point. If a civilisation is only 2500 years behind us, less than an eye blink in cosmological times, then they will be in the stone age and not really interested in radio though they will have the silicon chip albeit in a slightly different form :-) .

Even if life does exist within this finite range it will not necessarily be "intelligent". The dinosaurs would still be ruling this planet had it not been for an unfortunate meeting with a space borne lump of rock that let the underlings evolve.

So with a total number of predicated life supporting systems set at 10000 randomly seeded around our galaxy at various stages of development it seems that to search for them is a waste of time, money and man/woman power. Surely there are more beneficial lines of research that should be followed.

I am happy to see that the discussion points to adding other sorts of technological channels to the SETI mission.I have done my own calculations that point to perhaps a Trillion Earth-like planets out to 15 Billion LY from Earth. If one in a million have 'civilizations' comparable to ours then there are still a MILLION out there. Perhaps a few have transcended their warlike and selfish tendencies, giving them a far better chance of finding US than we of them.The fact they haven't tells us that Space is quite VAST and even they have not solved the problems of routine space travel and effective intra and intergalactic communication. • Think carefully and you will see that just the presence of liquid water is insufficient! What distinguishes EARTH is its rather peculiar ATMOSPHERIC COMPOSITION.Aside from O2 this is not at all well understood. But I did build my own transmitter and sent the same message every night for 20 years: IS ANYONE ELSE OUT THERE? Finally, last month I was excited to recieve this cryptic reply: " NO! THERE'S NOBODY ELSE OUT HERE. YOU ARE ALL ALONE IN THE UNIVERSE! NOE STOP PESTERING US!"

I am happy to see that the discussion points to adding other sorts of technological channels to the SETI mission.I have done my own calculations that point to perhaps a Trillion Earth-like planets out to 15 Billion LY from Earth. If one in a million have 'civilizations' comparable to ours then there are still a MILLION out there. Perhaps a few have transcended their warlike and selfish tendencies, giving them a far better chance of finding US than we of them.The fact they haven't tells us that Space is quite VAST and even they have not solved the problems of routine space travel and effective intra and intergalactic communication. • Think carefully and you will see that just the presence of liquid water is insufficient! What distinguishes EARTH is its rather peculiar ATMOSPHERIC COMPOSITION.Aside from O2 this is not at all well understood. But I did build my own transmitter and sent the same message every night for 20 years: IS ANYONE ELSE OUT THERE? Finally, last month I was excited to recieve this cryptic reply: " NO! THERE'S NOBODY ELSE OUT HERE. YOU ARE ALL ALONE IN THE UNIVERSE! NOE STOP PESTERING US!"

One problem with all this is the duration of an advanced civilization, even assuming it to be radio 'noisy'. If a civilization can last for 10,000 years, a long time for our kind of civilizations here, that means if you are on the opposite side of our galaxy, there is a 10,000 year long wavefront of energy from say, 100,000 LY away.

It sweeps through the galaxy and reaches us. Since our sun has been around for less than 5 billion years and the galaxy is over 10 billion years old, and assuming it takes 5 billion years for our level of life to appear on any given sun with the proper resources, enough metals, water, etc., then there is time enough from 5 billion years ago to now to have had a half million such wavefronts to have come and gone.

So here we come 10 or 12 billion years later, looking for such signals. The problem could be put down to simple luck. We have to be in the right place AND the right time to pick up signals from any given 10,000 year long wavefront.

We may have had the poor luck to have had the tail end of that 10,000 year front gone by us in the year 1900, for instance. We would not have had a chance to ever have picked that one up no matter how sensitive our equipment.

So that is a good reason why we may never hear such signals. We would have to be extraordinarily lucky.

What I would do

If I wanted to get the idea across to an alien intelligence that I am also intelligent I would start by playing music. There is a sewage treatment plant in Germany which plays Mozart to the bacteria and they respond (saving the company money due to the faster metabolism).

Another thing I would try, in the long term, is to encode a message, such as a sequence of prime numbers, into DNA, insert this into a bacteria and drop the bacteria on to some planet.

2 cents

We can't even tolerate a human being from across the border. If I was an intelligent out world specie I wouldn’t contact humans with a ten lights years long pole. Instead, we are risking the wrong beings to come. I am a sci-fi fan, but I have to reluctantly agree with Professor Stephen Hawking on that one. By the other hand, if we contact other beings before they come, it would have a strong coalescing effect on us humans. In addition, to map possible earthlike planets will be useful to prepare us for when, sooner or later, for whatever reason we abandon earth.

SETI

How can we be detected at 100 parsecs when we've been emitting for only 100 years? Isn't the speed of light the speed limit?

Actually, I think it is a lot worse than it might seem. Remember, the first radio was rather low power and at low frequencies which are nearly totally absorbed in the atmosphere and reflected by the ionosphere. I doubt that any of that would be detectable at the closest star, about 4 light years. Even TV which is high power and high enough frequency to get through is beamed toward the horizon and spread over 360 degrees. Given the Earth's rotation, only a minute portion of that seemingly powerful signal would sweep across an antenna on a distant planet being detectable, if at all, for only a brief period of time a couple times in an Earth day. Today, other than amateur operators, we are using less of HF, VHF and UHF transmission and more cable, especially for international communications. We are already becoming quiet. I see no reason to expect other civilizations to do differently.

If there are any true space faring civilizations, they would need very different communications systems providing essentially real-time response. We have not yet discovered these, if they even are possible. I doubt that anything other than a high power beacon directed toward a likely target could ever be detected at a receiver light years away.

I support the SETI operation and hope they find something. I do not expect that they will unless someone at the other end wants to be detectred, and they do conduct a lot of radio astronomy along with the SETI work, so the effort is certainly not being wasted.

Scatter-shot is Harder

It may seem like a long-shot, but a dedicated stare at the Andromeda galaxy may be the most promising way to detect signals from advanced civilizations already in mutual communication with advanced civilizations in our galaxy. Instead of a tedious spot-by-spot search within their own galaies, such galactic civilizations may complement each other, not just by examining the other's galaxy for new technical civilizations that arise like ours, but to provide a constant and relatively strong beamed beacon signal at each other to make it much easier for young civilizations to discover them. Who knows? There may be an unimaginable amount of information available on the state of our galaxy a 'short' 4 million years old (round-treip time at the speed of light), letting us know, for example, the locations of 'known' technical civilizations within OUR galaxy to tune into. It wouldn't matter that the hypothetical Andromedans wouldn't learn of our existence for another few million years. They'll have already provided the key to allow us to find our neighbors in our own galaxy. And, if we learn to be wise enough, we might survive sustainably and long enough to join the club.

Extra data favours SETI

Using the inverse square law and communications data from the Pioneer spacecraft when last contacted, I estimated the range of TV signals as 4 light-days, increasing to several light-years for pure carrier detection. Of course, the SKA is a bigger receiving aerial, so the ranges are greater. But such estimated ranges may be dwarfed by:(a) refraction and ducting of waves through interstellar gas clouds and magnetic fields, giving much longer range propagation paths.(b) signals passing through space plasma might be boosted by maser amplification.

Although civilizations like ours may be radio-loud only for a century because of increasing communications efficiency, this depends upon increased computer power, and with Moore's law operating, communication such as pseudo-random noise modulation, may compensate for decreasing transmitter power - see linas.org…seti.html

Advanced civilizations may be making gigawatt RF power directly from fusion, or be modulating natural transmitters, like their aurorae, emitting billions of watts of kilometric radiation. If the closest pairs of ETI civilizations are the first to communicate with each other, their stray signals, along with similar signals from natural sources, like rapid pulsars, may be detectable here.

Marconi was told he couldn't span the Atlantic using wireless. Against the odds, he succeeded. In the USA - historically the stronghold of amateur radio (and SETI) - amateurs had been assigned a wavelength of 200 metres, because "it's no good for anything; they'll never get out of their own back yards with it." (ARRL Handbook 1936) But amateurs pioneered DX (long distance communication) and SETI now has its parallels. Far from being 'a waste of resources', with so much hobbyist and public interest, training young optimistic persons in all the technical, scientific and other subjects that SETI requires, is potentially hugely beneficial to society, whether or not ETI signals are eventually received. G3RVU

Pure speculation as many as the Astrophysics concepts. Just constructions over images seeing that far that nobody can really tell if its still exist or not and the worst part, whithout the technology to prove a damn thing. Nonsense action, and useless effort.

Slim odds

I really think what SETI is doing is not science,but faith,and I resent my tax dollars being spent on this enterprise.True science is built on predictive theorization which in turn depends on the collection of hard data.The SETI organization is built on speculation from the ground up.I am reading a book written by Paul Davies,The Eerie Silence,which injects some reason into this subject.